A221818 Number of 2 X n arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor, without move-in move-out straight through or left turns.

0, 4, 16, 91, 459, 2429, 12678, 66380, 347305, 1817234, 9509123, 49756006, 260353922, 1362310931, 7128385902, 37299670925, 195172780250, 1021252966367, 5343766480365, 27961572573739, 146310575925354, 765578706008096

Offset

1,2

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = a(n-1) +17*a(n-2) +25*a(n-3) +7*a(n-4) +15*a(n-5) +10*a(n-6) -19*a(n-7) +8*a(n-8) +9*a(n-9) +2*a(n-10) -3*a(n-11) +a(n-12).

Example

Some solutions for n=3
..1..1..1....1..1..0....1..1..0....0..3..1....0..2..0....1..2..1....0..1..1
..0..3..0....0..3..1....1..3..0....1..1..0....1..2..1....0..2..0....1..3..0

Crossrefs

Row 2 of A221817.

Sequence in context: A013030 A124962 A292088 * A331648 A009568 A139155

Adjacent sequences: A221815 A221816 A221817 * A221819 A221820 A221821

Keyword

nonn

Author

R. H. Hardin, Jan 26 2013

Status

approved